They say three police were wounded in the Sunday ambush in the town of Sheik Zuwayed on the road to Rafah on the border with Gaza.

The gunmen fled after clashing with troops while the wounded were transferred to hospital in critical condition.

Security officials spoke on condition of anonymity because they were not authorized to speak to journalists.

Insurgent attacks in the Sinai have surged in the nine months since the military ousted Islamist president Mohammed Morsi.

On Saturday, a Palestinian official says Egypt has reopened its border with the Gaza Strip after weeks of closure.

Hamas’ Interior Ministry spokesman, Eyad al-Bozum, says Egyptian authorities opened the Rafah border crossing Saturday after it was closed for 49 days. He says it will remain open for three days and that there are about 6,000 Gazans seeking to cross into Egypt, including patients, students and people whose residence visas are close to expiring.

Egypt has only sporadically opened the crossing for select humanitarian cases since the ouster of Morsi. The Egyptian military has imposed tough border restrictions on Gaza’s Hamas rulers, who have close ties to its rival Muslim Brotherhood, including sealing smuggling tunnels and blocking passenger traffic.